468 ANNUAL REPORT OF THE Off. Doc. 



of iron. Dr. Spurr has observed that: "In shale beds, there is 

 always a considerable percentage of iron. This usually combines 

 with the sulphur contained in organic matter to form sulphide of 

 iron (pyrite)." Some of it is probably of igneous origin. 



OCCURRENCE 



Iron pyrite is a very widely disseminated mineral. It occurs in 

 rocks of all varieties and in all geological formations, from the earli- 

 est to latest, usually and unfortunately, however, in quantity or 

 amount too small to make its separation a profitable undertaking. 

 It may occur as bedded or vein deposits, or sporadically, as crystals 

 in cubic form or some of its modifications; as nodules or lentils, in 

 thin flakes or small particles throughout, slates, shales, schists, sand- 

 stones, etc. It is also found in coal beds, sometimes appearing as 

 nodules; as partly separating the coal benches either as hard 

 masses or intermixed with the mineral charcoal bands so often found 

 in coal beds and known to the miners as ''Mother of Coal," Again, it 

 may be found in flakes as thin as the finest tissue paper adhering to 

 the coal, along lines parallel to or at right angles to the planes of 

 stratification in joints, where sometimes are found thin slabs, perhaps 

 a foot or more in length covered with small cubic crystals, with a 

 brilliance almost equal to that of cut diamonds. Its presence in 

 coal is always detrimental and, in extreme cases, so much so that 

 for either the manufacture of coke for metallurgical purposes, the 

 use of such coal is precluded, because of the increase in sulphur con- 

 tent of the coal due to its presence. 



The deposits of this mineral of economic value, now being exploited 

 in the Eastern United States, seem to lie, geologically, in a belt of 

 the Pre-Cambrian metamorphic rocks, extending, according to Prof. 

 Reis, from New Hampshire to Alabama. The principal sources of 

 domestic supply are in New York, Virginia, Missouri, California and 

 Wisconsin, (In the latter state, the pyrite is separated from zinc 

 blende by electrostatic methods;) while as a by-product in coal 

 mining, Ohio, Indiana and Illinois produced 47,486 long tons in 1913. 

 The production of pyrites in Pennsylvania has been very small and 

 was limited to by-products of coal mining and not from distinct op- 

 erations for the production of this mineral only. 



GENERAL DESCRIPTION 



Pyrite (Bisulphide of Iron) is a mineral of brassy yellow color; 

 it is often found in the form of a cube, sometimes as an octahedron 

 (8 sided) and as a five edged twelve sided crystal known as the 

 pyritohedron or other forms of the isometric system. Again, it may 

 occur in crystalline masses which may assume any form; sometimes 

 it appears in the form of a bunch of grapes or botryoidal; again, it 

 may be globular or in stalactitic form. It is extremely hard and 

 brittle. In the scale of hardness, it ranges from 6 to 6.5, that is to 

 say, it is harder than orthoclase (feldspar) and not quite as hard as 

 quartz. The streak it leaves, after being rubbed on an unglazed 

 porcelain or other white surface, is greenish to brownish black. It 

 is opaque or impervious to rays of light, no matter how thin the 

 piece may be. Its specific gravity is 4.9 to 5.2, being less than one- 

 third as heavy as gold (19.26) and about one-half as heavy as silver 

 (10.5). If the faces or sides be carefully examined it will be noticed 



